Tests of seawater near Japan’s Fukushima nuclear power plant have not detected any radioactivity, the environment ministry said on Sunday (Aug 27), days after authorities began discharging into the sea treated water used to cool damaged reactors.
Japan started releasing water from the wrecked Fukushima plant into the Pacific Ocean on Thursday, sparking protests within Japan and neighbouring countries, in particular China, which banned aquatic product imports from Japan.
Japan and scientific organisations say the water is safe after being filtered to remove most radioactive elements except for tritium, a radioactive isotope of hydrogen.
UV radiation is quite damaging (although part of the popular “summer tan” culture) on its own. However, we also receive higher energy photons (above UV: xray, gamma) as well as some energetic muons from the sun. You get a 4x of a daily dose of radiation if you grab a flight. Around that of an xray. All of which is mostly ignored by people.
You are correct that gamma ray radiation is by far the most damaging radiation. Beta and alpha radiation can be stopped by pieces of paper (or your skin), gamma radiation will go through your house, your car, your wife, hit a dna molecule in your hair follicle, and make that hair follicle permanently gray.
More interestingly, putting the “radioactive” seawater in perspective: tritium fizzles into some beta radiation, of 18kev energy. Assuming, magically, all this (beta radiation) energy was deposited perfectly into your DNA (nearly impossible because it is beta radiation), resulting in maximal damage, in somewhere important and not the dead layer of your skin, doing a tiny calculation we can compute this damage to be that of a photon of 0.07nm wavelength (18 kev), of similar energy used in simple xray imaging (CT imaging uses 5x higher energy). With 10 becquerels / liter, 100 liters of water surrounding you, could inflict a horrible dose of 24 (hours) * 3600 (sec / hour) * 10 x 100 x 18 kev * 1.60218e-16 (Joule / kev) / 70 (kilograms per human) = 3.55958619e-9 Sv in a day
That is a terrifying amount of 3.6 nSv. Almost close to 1/20 that of a banana you eat (I am not joking, just smiling heavily).
Fun facts: https://xkcd.com/radiation/
The fact that people talk about radioactivity in this news, and chinese being angry and the world going apeshit is… unfathomable.